Introduce MIDIInputMap and MIDIOutputMap.

Source/bindings/core/v8/V8Binding.h

Index: Source/bindings/core/v8/V8Binding.h
diff --git a/Source/bindings/core/v8/V8Binding.h b/Source/bindings/core/v8/V8Binding.h
index 4c57f6efec798422a1517e29cc192a35c6e50f9a..6765c205918dcbf30440436df65247368444be8e 100644
--- a/Source/bindings/core/v8/V8Binding.h
+++ b/Source/bindings/core/v8/V8Binding.h
@@ -960,6 +960,17 @@ private:
     v8::TryCatch& m_block;
 };
 
+// Returns an object representing {done: true, value: undefined}.
+v8::Local<v8::Value> v8DoneIteratorResult(v8::Isolate*);
+
+// Returns an object representing {done: false, value: |value|}.
+v8::Local<v8::Value> v8IteratorResult(v8::Isolate*, v8::Handle<v8::Value>);
+template <typename T>
+v8::Local<v8::Value> v8IteratorResult(ScriptState* scriptState, const T& value)
+{
+    return v8IteratorResult(scriptState->isolate(), V8ValueTraits<T>::toV8Value(value, scriptState->context()->Global(), scriptState->isolate()));
+}
+
 } // namespace blink
 
 #endif // V8Binding_h